Joyce Carol Oates has defended herself against Julian Barnes's accusation that her failure to mention her remarriage a year after her husband's death in her memoir of widowhood will cause some readers to feel "they have a good case for breach of narrative promise".

But "there is something unhappy" in the prolific American novelist's omission to mention the fact that she was remarried in March 2009, writes Barnes, with Oates only hinting "rather coyly on the last page" about her new husband's existence. "She is writing about a year that began on February 18, 2008; we know from her own mouth (in an interview with the London Times) that she met her second husband in August 2008, they started going on walks and hikes in September, and were married in March 2009," writes Barnes, whose own wife, the literary agent Pat Kavanagh, died in October 2008.

Pointing to the concluding statement of A Widow's Story, that "of the widow's countless death-duties there is really just one that matters: on the anniversary of her husband's death the widow should think I kept myself alive", Barnes wonders "if she is also thinking 'I might be getting married in a few weeks' time', does this not change the nature of that statement?"

"This isn't a moral comment: Oates may quote Marianne Moore's line that 'the cure for loneliness is solitude', but many people need to be married, and therefore, at times, remarried," he says. "However, some readers will feel they have a good case for breach of narrative promise."

Oates has now moved to defend herself in a letter published in the new issue of the New York Review of Books, in which she says that A Widow's Story "was not meant to be an autobiographical work, which would include many, many developments in the memoirist's life subsequent to the early experience of widowhood, but rather an intimately detailed account of the raw, early weeks and months of 'widowhood' – so much of this time is derangement, wild (and pathetic) rationalising, the constant challenge of 'getting through a day'."

She was hoping, she says, to record "the original experience of loss and grief ... in a visceral way unmediated by a retrospective vision", and the fact that she remarried 13 months after her husband's death "did not seem that relevant or crucial".

"A memoir is most helpful when it focuses upon immediate experience, not a clinical, subsequent summation from what would be the 'future' of the individual in the throes of an unpredictable and uncontrollable experience," writes Oates. "It is not a charge against grief that it can't last as pure, raw grief for very long – as one who is tortured, but survives, has not been less tortured because she has survived."

Nonetheless, Oates now feels that she "should have added something like an appendix" to bring her personal story up to date, and hopes to do this for future editions of A Widow's Story. "Since nothing seems to arouse reproach in reviewers quite so much as the possibility that the memoirist is less miserable at the time of the writing and afterward than she was at the time of the experience about which she is writing, it is only sensible to include an appendix to remedy this, which I will hope to do," concluded the author.

But her editor, Ecco publisher Daniel Halpern, is not best pleased. "I completely disagree, and I thought I had talked her out of that," he told the New York Times. "She wrote a book about what it's like to be in limbo – about what it was like to lose the man she had been married to all her life. Why include the next husband? That's not what the book is about. What is she supposed to say – that she finally met someone and got married? That certainly breaks the spell of the book, which is written differently and perceived differently from anything she's ever done before."